Adjustable stylet

ABSTRACT

An adjustable stylet includes a core wire having a portion surrounded by a compression member preferably comprised of a flat wire spring. Depending upon the configuration, compression or relaxation of the compression member in response to forces at the tip or handle of the stylet results in adjustments to the characteristics of the stylet. In a first embodiment, the stiffness of the stylet is adjustable. In a second embodiment, the length of the stylet is adjustable. In a third embodiment, both the stiffness and the length of the stylet are adjustable.

FIELD OF THE INVENTION

[0001] The present invention relates generally to the field ofintravascular leads and catheters. More specifically, the presentinvention relates to an adjustable stylet for use in positioning suchleads and catheters.

BACKGROUND OF THE INVENTION

[0002] Stylets and guidewires are used to control the manner in whichintravascular leads and catheters are introduced into the veins orarteries of the body. Although both kinds of devices are often thoughtof as simply very small wires, the purpose and operation of stylets issignificantly different as compared to guidewires.

[0003] Conventional intravascular procedures typically involve aninitial step of introducing and routing a guidewire through a patient'svascular system to provide a rail or track along which additionalintravascular devices may be introduced. Once a guidewire is in place, asheath is routed over at least a portion of the guidewire to provide alarger opening into the vein or artery and sometimes to protect theinside walls of the vessels along the route of the guidewire. With thesheath in place, the guidewire may be removed or may remain in place asadditional intravascular devices such as intravascular leads andcatheters are introduced into the patient's vascular system.

[0004] To better accomplish the purpose of a guidewire of providing atrack along the patient's vascular system for other intravasculardevices, it is desirable that the guidewire have a region at the tip ofthe guidewire, referred to as the distal end, that is extremelyflexible. Preferably, the guidewire has the ability to vary theflexibility of the distal tip and/or deflect the distal tip so as to aidin routing the guidewire through the patient's vascular system. U.S.Pat. Nos. 4,215,703, 4,456,017, 4,719,924, 4,886,067 and 5,060,660describe designs for guidewires that use an internal tensioning memberor pull wire to alter the characteristics of the non-expandable distaltip and/or to deflect the distal tip. U.S. Pat. Nos. 4,271,8454,822,345, 5,605,162, 5,762,615, 5,851,203, 5,957,903 and 6,183,420describe various designs for guidewires with adjustable stiffness bymoving a core member axially within the distal region of the guidewire.U.S. Pat. Nos. 5,938,623 and 6,039,743 describe a guidewire withadjustable stiffness that is controlled by running electricity through amemory metal wire tip. U.S. Pat. No. 5,341,817 describes a guidewireextension arrangement in which a smaller inner extension can be pushedout of a larger core segment to extend the distal end of the guidewire.U.S. Pat. Nos. 4,846,174 and 5,338,301 describe guidewires with a coremember that can be extended to axially stretch an angioplasty balloon atthe distal tip. In a similar manner, U.S. Pat. Nos. 3,841,308 and4,759,748 describe catheters that utilize a core member to axiallystretch a coiled section at the distal end of the catheter for purposesof controlling delivery of a fluid.

[0005] In contrast to the guidewire which serves as a track over whichother intravascular devices are routed, a stylet is used within aninternal lumen of an intravascular device both to push that devicethrough the vascular system and to steer the device as it is beingpushed. Although some intravascular devices are designed to steerthemselves using internal pull wires, almost all leads, most cathetersand some guidewires have an inner channel or lumen into which a styletis inserted. In addition to pushing the intravascular device through thevascular system by engaging the distal end of the device, the styletalso serves to deflect the distal end of the intravascular device so asto steer the distal end through the vascular system. Unlike the lead,catheter or guidewire, which has a distal region that is flexible andfloppy, the stylet must be stiffer and more rigid so as to enable thestylet to push the lead or catheter through the patient's vascularsystem. Conventionally, stylets having different bends on the distal endare used at different points of advancing the lead or catheter to adesired location. For straight segments of a vessel a straight stylet isused, whereas a stylet with a curved distal tip is used to navigate thelead or catheter through a curved portion of a vessel. U.S. Pat. No.2,118,631 shows an early stylet formed of coils of flat wire welded toplugs at both ends that could be bent by the physician into either astraight or curved configuration at its distal end prior to insertioninto the lumen of a catheter or the like. In a more recent type ofstylet, an operator controls the direction of deflection of the tip ofthe stylet while it is in place in the lumen, which in turn controls thedirection of the cardiac lead or catheter as it is moved along the veinsor arteries. An example of a stylet with such a deflecting tip is shownin U.S. Pat. No. 5,824,031. Other examples of steerable stylets can befound in U.S. Pat. No. 5,873,842 and PCT Publ. No. WO 00/22981.

[0006] The more control and flexibility an operator has over anintravascular device, the easier it is to operate that device. In thecase of stylets, the physical demands of engaging the distal end of alumen of an intravascular device so as to push that device through thevascular system impose constraints on the beam strength of the devicethat are much different than the constraints encountered for aguidewire, catheter or lead. Most guidewires are constructed from atapered core wire with a coiled round wire wrapped around this taperedcore wire in order to achieve the necessary flexibility in the distalregion of the guidewire. Stylets, on the other hand, are generallyconstructed of a solid wire of uniform diameter without any coils aroundthis wire in order to achieve the necessary strength and rigidityrequired over the entire length of the device so as to function as astylet. Because of these differences, the techniques for improvingcontrol and flexibility that have been utilized for guidewires,catheters and leads are not generally applicable for the design ofstylets. It would be desirable to provide for a stylet with improvedflexibility and control without the need for changing stylets during aprocedure to obtain different orientations of the distal tip of thestylet.

SUMMARY OF THE INVENTION

[0007] The present invention is an adjustable stylet. The styletincludes a core wire having a portion surrounded by a compression memberpreferably comprised of a flat wire spring. Depending upon theconfiguration, compression or relaxation of the compression member inresponse to forces at the tip or handle of the stylet results inadjustments to the characteristics of the stylet. In a first embodiment,the stiffness of the stylet is adjustable. In a second embodiment, thelength of the stylet is adjustable. In a third embodiment, both thestiffness and the length of the stylet are adjustable.

[0008] Unlike most guidewires that are so flexible the guidewire willfall over when grasped only by the ends, the stylet in accordance withthe present invention requires a much greater rigidity such that thestylet forms an arc that generally stands up and does not fall over whenthe stylet is grasped only by the ends. The present invention utilizes acore wire that has a relatively uniform beam strength over its axiallength so as to provide the necessary rigidity and strength required fora stylet. The compression member augments the characteristics of thecore wire in a manner that is adjustable so as to also be able to moreclosely emulate the desired characteristics of an adjustable guidewire.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a side view of an adjustable stiffness stylet in arelaxed state.

[0010]FIG. 2 is a side view of the adjustable stiffness stylet of FIG. 1in a compressed state.

[0011]FIG. 3 is a side view of an alternative embodiment of theadjustable stiffness stylet.

[0012]FIG. 4 is a partial side view of an adjustable length stylet.

[0013]FIG. 5 is a cutaway partial side view of the adjustable lengthstylet of FIG. 4.

[0014]FIGS. 6a, 6 b and 6 c are side views of the component pieces ofthe adjustable length stylet of FIG. 4.

[0015]FIGS. 7 and 8 show cutaway partial sides views of alternateembodiments of the handle for the adjustable stiffness stylet of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0016] Referring to FIG. 1, an adjustable stiffness stylet 10 comprisesa stylet core wire 12, a space wound flat wire spring or compressionmember 14, a sliding handle 16 located at a proximal end 18 of the corewire 12 and a tip 20 of the core wire 12. Preferably, the compressionmember 14 is welded, crimped or otherwise secured to the core wire 12near the tip 20. Preferably, the space wound compression member 14 hasan inner diameter (I.D.) that is just slightly larger than the outerdiameter (O.D) of the core wire 12. Optionally, a cover tube (not shown)may be secured over the exterior so long as the tube does not interferewith the movement of compression member 14.

[0017] As the sliding handle 16 is pushed toward the tip 20, the handle16 makes contact with the proximal end of compression member 14 but doesnot slide over compression member 14. Compression member 14 iscompressed in response and the overall flexibility of the stylet 10begins to stiffen. As more force is applied to the handle 16, the openwindings of compression member 14 close and the stiffness of stylet 10is increased as shown in FIG. 2. When the desired stiffness is achieved,the operator may advance stylet 10 without altering the stiffness byapplying force to the proximal end 18 of the core wire 12 withoutdisplacing the position of handle 16 relative to the compression member14. Alternatively, handle 16 may be provided with locking mechanisms tolock the handle 16 in a given position relative to core wire 12, orproximal end 18 of the core wire 12 may be equipped with a separatehandle. Handle 16 preferably is slide operated along the longitudinalaxis of core wire 12, although it will be understood that handle 16 alsocould operate in a screw manner (as shown in FIG. 7) or ratchet manner(as shown in FIG. 8) along the longitudinal axis of core wire 12.

[0018]FIG. 3 shows an alternate embodiment of an adjustable stylet 22 inwhich a rigid tube 24 is located between the handle 16 and thecompression member 14. In this case, compression member 14 is secured tothe tip 20 of the core wire 12 and the resulting stylet has a flexibletip portion corresponding to the length of the core wire 12 surroundedby compression member 14. As the handle 16 is pushed toward the tip 20,the tube 24 is pushed into the proximal end of the compression member 14and the space wound coils of compression member 14 are compressed,thereby increasing the stiffness of the stylet 22.

[0019] Referring now to FIG. 4, a second embodiment of an adjustablestylet 30 comprises a proximal core wire 32, a compression member 34(FIG. 5), a distal core wire 36 and a cover tube 38. The cover tube 38is welded to the proximal core wire 32, but not to the distal core wire36. The compression member 34 is preferably a space wound flat wirespring that is welded, crimped or otherwise secured to the adjacent endsof the proximal core wire 32 and the distal core wire 36. As shown inFIGS. 6b and 6 c, the stylet core wire is preferably centerless groundat the adjacent ends of the proximal core wire 32 and distal core wire36 to all several turns of the compression member 34 to be centered oneach core wire 32, 36.

[0020] Preferably, the distal core wire segment 36 is relatively shortin comparison to the proximal core wire 32, although the lengths of thecore wire segments 32 and 36 may be various lengths. In this embodiment,the compression member 34 is compressed and the overall effective lengthof the stylet 30 is shortened in response to a compressive force exertedat the distal end of the distal core wire 36. The ability of the stylet30 to adjust in length reduces the need for stocking and maintaining avariety of different length stylets.

[0021] In a third embodiment, the stylet 30 is used as the core wire 12of the stylet 10 to combine both of the adjustable qualities of thepresent invention in a single embodiment.

[0022]FIGS. 7 and 8 show alternate embodiments for the handle of theadjustable stiffness stylet of FIG. 1 in partial cross-sectional views.In FIG. 7, the proximal end of the stylet core wire 39 is threaded toaccept a threaded handle 40. The stiffness of the stylet 10 is increasedby compressing the compressive member 14 through turning of the threadedhandle 40 clockwise to move the handle 40 away from the threadedproximal end of the stylet core wire 39. Similarly, the stiffness of thestylet 10 may be decreased by decompressing the compressive member 14through turning the threaded handle 40 counterclockwise toward thethreaded proximal end of the stylet core wire 39.

[0023] Referring now to FIG. 8, the proximal end 18 of the core wire 12of the adjustable stiffness stylet 10 is welded or otherwise secured tothe bottom part 41 of a multi-piece handle 42 that has a tongue 43. Thetongue 42 engages slots 44 of the top part 45 of a multi-piece handle42, which has an aperture 46 whose inside diameter is slightly largerthan the outside diameter of the stylet core wire 12 to allow the styletcore wire 12 to freely slide through the top part 45 of the multi-piecehandle 42. The stiffness of the stylet 10 is accomplished throughcompression of the compressive member 14 by pulling the bottom part 41of the multi-piece handle 42 toward the proximal end of the core wire 18in relation to the top part 45 of the multi-piece handle 42.Correspondingly, the stiffness of the stylet 10 can be decreased throughrelieving compression of the compressive member 14 by pushing the bottompart 41 of the multi-piece handle 42 away from the proximal end of thecore wire 18 in relation to the top part 45 of the multi-piece handle42. Once the desired stiffness of the stylet 10 has be accomplished byplacement of the top part 45 and bottom part 41 of the multi-piecehandle 42, the tongue 43 on the bottom part 41 engages a slot 44 on thetop part 45 of the multi-piece handle 42 to maintain the chosenstiffness.

[0024] The core wire 12 is preferably a stainless steel wire having anouter diameter of less than 0.020 inches and preferably in a rangebetween 0.005 and 0.018 inches and in the preferred embodimentapproximately 0.014 inches. Above this range, the diameter of the corewire is generally too large to effectively serve as a stylet forinsertion in the lumens of most intravascular devices. The physicalcharacteristics of core wire 12 must be suitable for use as a stylet, asopposed to use as a guidewire. Most importantly, the core wire 12 shouldhave a relatively uniform beam strength over its axial length so as toprovide the necessary rigidity and strength required for a stylet. Byrelatively uniform it is understood that manufacturing tolerances oreven minor variations in beam strength of less than about +/−10% wouldbe considered relatively uniform in terms of the beam strength of thecore wire. The tensile strength of the wire should be at least 150K psiand preferably in a range between 200K psi and 400K psi. Alternativewires suitable for core wire 12 include MP35N, AC10 tungsten, orNintonal. With existing technologies for wound wire or braided wire, itis not possible to utilize such wires for the core wire 12 in accordancewith the present invention because these wires do no exhibit the desiredcharacteristics. As such, the core wire 12 is preferably a solid roundwire having a relatively uniform cross-sectional diameter over its axiallength.

[0025] The compression member 14 is preferably a flat or ribbon wiremade of stainless steel or a similar material. The compression memberpreferably has an aspect ratio of at least 2:1. While the widercross-sectional dimension of the flat wire can vary anywhere above thelower range of the aspect ratio, preferably the narrow cross-sectionaldimension of the flat wire is less than 0.003 inches.

[0026] In the embodiment of the adjustable length stylet 30, theprinciple advantage of this feature is its use in those situations wherethe length of stylet must be held to very tight tolerances. Typically,the stylet 30 is inserted into an intravascular device within a sterilefield prior to insertion in the patient's vascular system with theproximal ends of the stylet 30 and intravascular device locked togetherwith a Luer lock or the like. In some applications, such as neurologicalapplications, the tolerances for the match between the length of thelumen of the intravascular device and the length of the stylet 30 mustbe within less than 0.010 inches. The ability to adjust the length ofthe stylet 30 reduces the need for tight tolerance matches between theselengths, thereby affording more interchangeability between stylets andintravascular devices.

1. An adjustable stylet for use within a lumen of an intravasculardevice comprising: a core wire having a blunt distal end and a proximalend and having an outer diameter of less than 0.020 inches and arelatively uniform beam strength over an axial length of said core wire;a compression member having a distal end operably secured to said corewire and a proximal end axially movable along said core wire, saidcompression member comprising a flat wire space wound around at least aportion of said core wire with a wide dimension of said flat wireoriented axially and an axial spacing between successive windings ofsaid compression member; a handle operably mounted proximate saidproximal end of said core wire, said handle axially movable to operablyengage said proximal end of said compression member such that said axialspacing between at least a portion of said successive windings isadjusted by movement of said handle, whereby a stiffness of said styletis adjusted by operation of said handle.
 2. The adjustable stylet ofclaim 1 wherein said compression member is secured to said core wireproximate said blunt distal end of said core wire.
 3. The adjustablestylet of claim 1 further comprising a rigid tube member operablypositioned around said core wire between said proximal end of saidcompression member and said handle to transfer axial force applied bysaid handle to said compression member.
 4. The adjustable stylet ofclaim 1 wherein said flat wire is a stainless steel wire having anaspect ratio of at least 2:1 and having a narrow cross-sectionaldimension of less than 0.003 inches.
 5. The adjustable sylet of claim 1wherein said blunt end is comprised of a ball welded to said distal endof said core wire.
 6. The adjustable stylet of claim 1 wherein saidhandle is slidable relative to said core member.
 7. The adjustablestylet of claim 1 wherein said handle includes a handle member securedto said core wire proximate said proximal end and a moveable memberoperably engaged with said handle member such that said moveable memberis axially moveable relative to said handle member within a distancedetermined by said handle member, said moveable member including aproximal portion extending distally beyond said handle member foroperably engaging said proximal end of said compression member.
 8. Theadjustable stylet of claim 7 wherein said moveable member and saidhandle member include structure such that said moveable member isslidable relative to said handle member.
 9. The adjustable stylet ofclaim 7 wherein said moveable member and said handle member includestructure such that said moveable member is screwable relative to saidhandle member.
 10. The adjustable stylet of claim 7 wherein at least oneof said moveable member and said handle member includes structure toreleasably position said moveable member relative to said handle memberat multiple axial locations.
 11. The adjustable stylet of claim 1wherein said core wire comprises a wire having a uniform cross-sectionaldiameter.
 12. The adjustable stylet of claim 1 wherein said core wirecomprises a solid wire.
 13. The adjustable stylet of claim 1 whereinsaid core wire comprises: a first core wire segment and a second corewire segment; and a length adjustment member secured between adjacentends of said first and second core wire segments, said length adjustmentmember comprising a space wound wire with an axial spacing betweensuccessive windings of said length adjustment member such that an axialforce applied to at least one end of said length adjustment memberdecreases said axial spacing between at least a portion of saidsuccessive windings of said length adjustment member.
 14. An adjustablestylet for use within a lumen of an intravascular device comprising: afirst core wire and a second core wire, each core wire having an outerdiameter of less than 0.020 inches and a relatively uniform beamstrength over an axial length of said core wire; and a compressionmember secured between adjacent ends of said first and second corewires, said compression member comprising a space wound wire with anaxial spacing between successive windings of said compression membersuch that an axial force applied to at least one end of said compressionmember decreases said axial spacing between at least a portion of saidsuccessive windings.
 15. The adjustable stylet of claim 14 wherein saidcompression member is a flat stainless steel wire having an aspect ratioof at least 2:1 and having a narrow dimension of less than 0.003 inches.16. The adjustable stylet of claim 14 wherein each of said adjacent endsof said first and second core wires are centerless ground and saidcompression member overlaps and is secured to said centerless groundportion of said adjacent ends.
 17. The adjustable stylet of claim 14further comprising a cover tube surrounding at least a portion of saidcompression member and secured at only one end to one of said first andsecond core wires.
 18. An adjustable stylet for use within a lumen of anintravascular device comprising: a core wire having a blunt distal endand a proximal end and having an outer diameter of less than 0.020inches and a relatively uniform beam strength over an axial length ofsaid core wire; compression means for adjusting a stiffness of saidstylet, said compression means having a distal end operably secured tosaid core wire and a proximal end axially movable along said core wire;handle means for engaging said compression means to effect adjustment ofsaid compression means, said handle means operably mounted proximatesaid proximal end of said core wire.
 19. The adjustable stylet of claim18 further comprising a rigid tube member operably positioned aroundsaid core wire between said proximal end of said compression means andsaid handle means to transfer axial force applied by said handle meansto said compression means.
 20. The adjustable stylet of claim 18 whereinsaid core wire comprises a solid wire having a uniform cross-sectionaldiameter.